Anti-backflash LED drive circuit

Abstract

The invention discloses an anti-backflash LED drive circuit which comprises a power supply module, a drive control circuit, a starting circuit and an auxiliary power supply circuit. The power supply module converts an input voltage into a bus voltage; the driving control circuit adjusts the duty ratio of a field effect switch tube through a first control chip, and LED constant-voltage and constant-current output is achieved. The starting circuit adopts a negative-voltage turn-off device, and is switched on to supply power to the control chip during initial power-on; the auxiliary power supply circuit inductively generates alternating voltage through an auxiliary winding coupled by a power inductor, continuously supplies power to the control chip after rectification and filtering, triggers the negative voltage turn-off device to be turned off, and cuts off a power supply path of the starting circuit; after power failure, the negative-voltage turn-off device is maintained in a turn-off state, backward flowing of residual voltage of a bus is blocked, the inductor stops oscillation to stop auxiliary power supply, power supply of the control chip returns to zero along with discharging of the capacitor, and LED back flash is eliminated through double mechanisms. According to the invention, the technical problem of LED power-off flashing back in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of LED lamp power supply circuits, and particularly to an anti-backflash LED drive circuit. Background Art

[0002] Traditional LED drive power supplies generally have the "backflash" problem in light load or power-off scenarios, and the root cause lies in the design defect of the circuit energy release path. When the power supply is disconnected, the electric energy remaining in the main energy storage capacitor cannot be released quickly and completely, resulting in the subsequent drive circuit being repeatedly mis-triggered due to the gradual drop of the capacitor voltage, causing the LED lamp beads to flash intermittently before completely going out. Existing technologies usually rely on passive discharge resistor networks to accelerate capacitor discharge, but are limited by the contradiction between resistor power and resistance value selection: increasing the resistance value can reduce static loss, but it prolongs the discharge time, and the residual voltage may still backflow to the control chip power supply terminal through the parasitic loop; while reducing the resistance value speeds up the discharge rate, but introduces additional power consumption and heat generation, reducing the overall system efficiency. In addition, the traditional startup circuit and the main power supply circuit lack a dynamic isolation mechanism, and the startup resistor may still provide a small amount of current to the control chip after power-off, resulting in the subsequent circuit being accidentally restarted when the capacitor voltage fluctuates. Especially in light load conditions, due to the small load current, the capacitor discharge rate is further reduced, and the backflash phenomenon is amplified. Although some solutions avoid the problem by forcibly restricting the use of the power supply under light load, in actual applications, it is difficult for users to strictly follow the load matching requirements, resulting in potential reliability hazards always existing. Summary of the Invention

[0003] The main object of the present invention is to propose an anti-backflash LED drive circuit, aiming to solve the technical problem of LED power-off backflash in the prior art.

[0004] To achieve the above object, the present invention provides an anti-backflash LED driving circuit, comprising: a power supply module, a driving control circuit, a starting circuit, and an auxiliary power supply circuit; the power supply module is used to convert the input voltage into a bus voltage; the driving control circuit includes a first control chip, a first field-effect control switch tube, and a first power inductor; the input end of the first field-effect control switch tube is connected to the output end of the power supply module, the output end is connected to the LED load through the first power inductor, and the control end is connected to the driving end of the first control chip; the starting circuit includes a negative voltage cut-off device; the input end of the negative voltage cut-off device is connected to the output end of the power supply module, and the output end is connected to the power supply end of the first control chip; the auxiliary power supply circuit includes an energy conversion module that is energy-coupled with the first power inductor, and is used to convert the induced AC voltage into a DC voltage and supply power to the first control chip; when the voltage difference between the control end and the output end of the negative voltage cut-off device is lower than the cut-off threshold due to the DC voltage, the negative voltage cut-off device is turned off, and the first control chip is continuously powered by the auxiliary power supply circuit; when the power supply is cut off, the voltage difference between the control end and the output end of the negative voltage cut-off device remains lower than the cut-off threshold to maintain the cut-off state, blocking the power supply loop of the bus residual voltage to the first control chip. At the same time, the first power inductor stops oscillating, causing the auxiliary power supply circuit to lose the maintaining voltage, realizing the non-backflash extinguishing of the LED load.

[0005] Preferably, the starting circuit further includes a first diode, a first voltage-dividing resistor group, and a second voltage-dividing resistor group. The negative voltage cut-off device is a depletion-type NMOS transistor, and the first diode is a zener diode; the drain of the negative voltage cut-off device is connected to the output end of the power supply module through the first voltage-dividing resistor group, the gate is connected to the output end of the power supply module through the second voltage-dividing resistor group, and the source is connected to the power supply end of the first control chip; the gate of the negative voltage cut-off device is also connected to the cathode of the first diode, and the anode of the first diode is grounded.

[0006] Preferably, the energy conversion module includes an auxiliary winding that is magnetically coupled to the main winding of the first power inductor, and a rectifying and filtering circuit connected to the auxiliary winding.

[0007] Preferably, the rectifying and filtering circuit includes a second diode, a third diode, and a first resistor; the second diode is a zener diode, and the regulated voltage value of the second diode is greater than that of the first diode; the first end of the first auxiliary winding is connected to one end of the first resistor, the other end of the first resistor is connected to the anode of the third diode, the cathode of the third diode and the cathode of the second diode are commonly connected to the power supply end of the first control chip, and the anode of the second diode is grounded.

[0008] Preferably, the rectifying and filtering circuit further includes a fourth diode and a first capacitor; one end of the first auxiliary winding is connected to one end of the first resistor through the first capacitor, the second end of the first auxiliary winding and the anode of the fourth diode are commonly connected to the ground, and the cathode of the fourth diode is connected to the other end of the first resistor.

[0009] Preferably, the drive control circuit further includes a fifth diode, and the first field effect control switch tube is an enhanced NMOS tube; the drain of the first field effect control switch tube is connected to the output end of the power supply module, the gate is connected to the drive end of the first control chip, and the source is commonly connected to the input end of the main winding of the first power inductor with the cathode of the fifth diode, and the anode of the fifth diode is grounded.

[0010] Preferably, the drive control circuit further includes a sixth diode, a second resistor, a third resistor, and a fourth resistor; the anode of the sixth diode, one end of the second resistor, and one end of the third resistor are commonly connected to the gate of the first field effect control switch tube, and the other end of the second resistor is connected to the source of the first field effect control switch tube; the cathode of the sixth diode is connected to one end of the fourth resistor, and the other end of the third resistor and the other end of the fourth resistor are commonly connected to the drive end of the first control chip.

[0011] Preferably, the drive control circuit further includes a voltage sampling circuit and a current sampling circuit; the voltage sampling circuit includes a third voltage dividing resistor group and a fourth capacitor, and the third voltage dividing resistor group is connected across the output end of the main winding of the first power inductor and the ground; the voltage feedback end of the first control chip is connected to the sampling node of the third voltage dividing resistor group and grounded through the fourth capacitor; the current sampling circuit includes a fifth capacitor and a sixth resistor; one end of the sixth resistor is connected to the source of the first field effect control switch tube, and the other end is commonly connected to the current feedback end of the first control chip with one end of the fifth capacitor, and the other end of the fifth capacitor is grounded.

[0012] Preferably, a boost circuit is further included, and the boost circuit includes a second control chip, a second power inductor, a seventh diode, a second field effect control switch tube, and a sixth capacitor; the first input end of the second control chip is connected to the output end of the power supply module, the second input end is connected to the first end of the auxiliary winding of the second power inductor, and the drive end is connected to the gate of the second field effect control switch tube; the second end of the auxiliary winding of the second power inductor is grounded; the first end of the main winding of the second power inductor is connected to the output end of the power supply module, the second end is connected to the drain of the second field effect control switch tube and the anode of the seventh diode, the cathode of the seventh diode is connected to the positive electrode of the sixth capacitor, the source of the second field effect control switch tube is grounded, and the negative electrode of the sixth capacitor is grounded.

[0013] Preferably, the boost circuit further includes a seventh resistor, an eighth resistor, a seventh capacitor and an eighth diode; one end of the seventh capacitor is connected to the first end of the auxiliary winding of the second power inductor, and the other end is connected to one end of the seventh resistor and one end of the eighth resistor; the other ends of the seventh resistor and the eighth resistor are commonly connected to the anode of the eighth diode, and the cathode of the eighth diode is connected to the second input end of the second control chip.

[0014] The present invention provides an anti-backflash LED driving circuit. In the startup stage, by utilizing the inherent conduction characteristic of the negative voltage turn-off device, the bus voltage can quickly supply power to the control chip without external drive, and a small-value voltage-dividing resistor is used to shorten the startup time, solving the delay problem caused by a large-value resistor in the traditional solution; during the operation stage, the auxiliary winding coupled by the inductor continuously supplies power to the control chip, and triggers the negative voltage turn-off mechanism of the negative voltage turn-off device, completely cutting off the power supply path of the startup circuit, eliminating the static loss of the voltage-dividing resistor, and improving the overall efficiency; after power-off, the negative voltage turn-off device maintains the off state under the negative voltage difference between the gate and the source, physically blocking the path of the residual voltage of the bus from flowing back to the control chip. At the same time, the main inductor stops oscillating, causing the auxiliary winding to lose power, and the rectifying and filtering circuit stops outputting. The power supply of the control chip naturally discharges with the energy storage capacitor and gradually returns to zero. The dual mechanisms ensure that the driving circuit is completely turned off, avoiding the intermittent restart of the LED lamp beads caused by the residual energy of the capacitor.

[0015] Furthermore, by setting a zener diode between the gate and source of the negative voltage shutdown device, the triggering threshold of the negative voltage shutdown can be accurately set by clamping the gate voltage fluctuation, avoiding mis-conduction or delayed shutdown problems caused by voltage fluctuations. Especially in the scenarios of input voltage transients or lightning surges, it ensures that the negative voltage shutdown device still operates reliably under abnormal working conditions, further strengthening the safety isolation ability during the power-off stage, enabling the system to maintain the non-flashback characteristic in a complex electromagnetic environment; the voltage-dividing resistor group adopts a multi-stage series structure. By increasing the number of resistors and optimizing the resistance ratio, the error influence of a single resistor is reduced to less than 1 / 4 of the total error, significantly improving the voltage sampling accuracy; through the magnetic coupling design of the auxiliary winding and the main winding and the synergistic effect of the rectifier and filter circuit, the energy conversion efficiency and power supply stability are improved; the voltage-doubling rectifier structure and the multi-stage filter capacitor combination in the auxiliary power supply circuit can generate a stable VCC voltage even when the voltage amplitude of the auxiliary winding fluctuates through the synergistic effect of capacitor coupling and resistor voltage division. It can not only improve the voltage stability of the auxiliary power supply, but also expand the input voltage range through the voltage-doubling mechanism, enabling the system to maintain the power supply of the control chip even at low input voltages, avoiding accidental shutdown caused by input voltage drop; the driving circuit suppresses voltage spikes through the freewheeling of the fifth diode. The sixth diode and the resistor network cooperate to accelerate the turn-off of the MOS transistor and suppress oscillations. Combining the rapid release of inductive energy and the negative voltage shutdown to block the reverse injection path, the power-off flashback is eliminated; high-precision constant voltage and constant current control is achieved through the cooperation of the voltage-dividing resistor group and the source resistor. The multi-stage voltage-dividing resistors are connected across the output terminal and combined with the filter capacitor to suppress noise to stabilize the voltage. The current sampled by the source resistor is filtered by the capacitor in real time to limit the current to prevent overload; the boost circuit realizes a stable high-voltage output under wide voltage input through the cooperative design of closed-loop control and the auxiliary winding. The second control chip dynamically adjusts the duty cycle of the MOS transistor to maintain the output voltage constant, adapting to the high-voltage LED driving requirements; the auxiliary winding combines with the voltage-doubling rectifier circuit to continuously supply power to the control chip, replacing the traditional starting resistor structure, eliminating static losses and improving efficiency. The capacitor coupling and resistor voltage division network suppress interference to ensure accuracy. Brief Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 It is the circuit schematic diagram of the anti-flashback LED driving circuit provided by an embodiment of the present invention; Figure 2 For Figure 1 the circuit schematic diagram of the starting circuit in Figure 3 is Figure 1 the circuit schematic diagram of the auxiliary power supply circuit in Figure 4 is Figure 1 the circuit schematic diagram of the drive control circuit in Figure 5 is Figure 1 the circuit schematic diagram of the boost circuit in

[0018] In the attached drawings: 1 - power supply module, 2 - drive control circuit, 21 - first control chip, 22 - first field - effect control switch tube, 23 - first power inductor, 24 - voltage sampling circuit, 25 - current sampling circuit, 3 - startup circuit, 31 - negative voltage cut - off device, 4 - auxiliary power supply circuit, 41 - first auxiliary winding, 42 - rectifier filter circuit, 5 - boost circuit.

[0019] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the attached drawings. Specific embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the attached drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present invention.

[0021] It should be noted that if there are directional indications in the embodiments of the present invention, such as up, down, left, right, front, back, etc., then the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0022] In addition, if there are descriptions such as "first", "second", etc. in the embodiments of the present invention, then the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those skilled in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] The main object of the present invention is to propose an anti - flashback LED drive circuit, aiming to solve the technical problem of LED power - down flashback in the prior art.

[0024] As Figures 1 to 4 shown, the present invention provides an anti-backflash LED driving circuit, which includes a power supply module 1, a driving control circuit 2, a starting circuit 3 and an auxiliary power supply circuit 4; the power supply module 1 is used to convert the input voltage into a bus voltage; the driving control circuit 2 includes a first control chip 21, a first field effect control switch tube 22 and a first power inductor 23; the input end of the first field effect control switch tube 22 is connected to the output end of the power supply module 1, the output end is connected to the LED load through the first power inductor 23, and the control end is connected to the driving end of the first control chip 21; the starting circuit 3 includes a negative voltage cut-off device 31; the input end of the negative voltage cut-off device 31 is connected to the output end of the power supply module 1, and the output end is connected to the power supply end of the first control chip 21; the auxiliary power supply circuit 4 includes an energy conversion module that is energy-coupled with the first power inductor 23, and is used to convert the induced AC voltage into a DC voltage and supply power to the first control chip 21; when the voltage difference between the control end and the output end of the negative voltage cut-off device is lower than the cut-off threshold due to the DC voltage, the negative voltage cut-off device is turned off, and the first control chip is converted to be continuously powered by the auxiliary power supply circuit; when the power supply is cut off, the voltage difference between the control end and the output end of the negative voltage cut-off device remains lower than the cut-off threshold to maintain the cut-off state, blocking the power supply loop of the bus residual voltage to the first control chip, and at the same time the first power inductor stops oscillating, causing the auxiliary power supply circuit to lose the maintaining voltage, realizing the non-backflash extinguishing of the LED load.

[0025] See Figure 1, in a specific embodiment of the present invention, the anti-backflash LED driving circuit includes a power supply module 1, a driving control circuit 2, a starting circuit 3, and an auxiliary power supply circuit 4. The power supply module 1 is connected to the input end of the rectifier bridge BG1 from the AC input end through the fuse F1 and the varistors RV1 / RV2. The DC output end of the rectifier bridge BG1 outputs the bus voltage after being filtered by the common mode inductors LF1 / LF2, the toroidal inductor L1, and the capacitor C4. The driving control circuit 2 includes a first control chip 21, a first field effect control switch tube 22, and a first power inductor 23. Among them, the first control chip 21 uses the integrated circuit U1 of the model BP3519, the first field effect control switch tube 22 is an enhanced NMOS tube Q1, and the first power inductor 23 is the main winding of the power inductor T1; the drain of the first field effect control switch tube 22 is connected to the bus voltage output end of the power supply module 1, the source is connected in series with the main winding of the first power inductor 23 to the LED load, and the gate is connected to the driving end Gate pin of the first control chip 21. The negative voltage turn-off device 31 of the starting circuit 3 is a depletion-type NMOS tube Q2, the drain is connected to the bus voltage output end of the power supply module 1 through a voltage dividing resistor, the gate is connected to the bus voltage output end of the power supply module 1 through a voltage dividing resistor, and the source is directly connected to the VCC pin of the first control chip 21. The energy conversion module of the auxiliary power supply circuit 4 is energy-coupled to the first power inductor 23, converts the induced AC voltage into a DC voltage, and is connected to the VCC pin of the first control chip 21 for power supply. The working process is as follows: When power is initially applied, the negative voltage turn-off device 31 (depletion-type NMOS tube) naturally conducts due to its inherent characteristics, and the bus voltage output by the power supply module 1 directly provides initial electrical energy for the power supply terminal of the first control chip 21 through the starting circuit 3; after the first control chip 21 is started, it drives the first field effect control switch tube 22 to periodically switch the conduction state, so that the main winding of the first power inductor 23 generates an alternating current, the energy conversion module induces an AC voltage to be converted into a DC voltage, and is fed back to the power supply terminal of the first control chip 21, resulting in a negative voltage difference between the gate and the source of the negative voltage turn-off device 31, triggering its turn-off, thereby cutting off the power supply path of the starting circuit 3 and completely switching the power supply of the first control chip 21 to the auxiliary power supply circuit 4. After power-off, the bus capacitor of the power supply module 1 slowly discharges through the discharge resistor, and the residual voltage still exists at the bus terminal. At this time, the negative voltage turn-off device 31 maintains the turn-off state due to the gate-source negative voltage difference, completely blocking the power supply path of the starting circuit 3 to the first control chip 21; at the same time, the main winding of the first power inductor 23 stops vibrating due to no driving current, the first auxiliary winding 41 cannot induce an AC voltage, the rectifying and filtering circuit 42 stops outputting, and the voltage at the power supply terminal of the first control chip 21 continuously decreases as the energy storage capacitor discharges naturally until the driving circuit is completely turned off. During this process, due to the physical turn-off characteristic of the negative voltage turn-off device 31 in the starting circuit 3, it is impossible to re-establish the power supply path through the bus residual voltage, completely eliminating the risk of mis-triggering of the subsequent circuit caused by the slow release of capacitor energy.

[0026] It can be understood that in this embodiment, through the negative voltage shutdown characteristic of the negative voltage shutdown device 31 and in combination with the dynamic power supply switching mechanism of the startup circuit 3 and the auxiliary power supply circuit 4, the LED driving circuit realizes non-flashing operation. Specifically: In the startup stage, since the negative voltage shutdown device 31 is a depletion-type NMOS transistor Q2, its inherent conduction characteristic enables the bus voltage to quickly supply power to the first control chip 21 without additional driving. Coupled with the design of a small-value voltage-dividing resistor, the startup time is significantly shortened, solving the startup delay problem caused by large-value resistors in the traditional solution; In the operation stage, the auxiliary power supply circuit 4 induces energy through the first auxiliary winding 41 to continuously supply power to the first control chip 21, and at the same time triggers the negative voltage shutdown of the negative voltage shutdown device 31, completely cutting off the power supply path of the startup circuit 3, eliminating the static loss of the voltage-dividing resistor, and improving the system efficiency; In the power-off stage, the negative voltage shutdown device 31 maintains the off state under the negative gate-source voltage difference, physically blocking the path for the residual voltage of the bus to pour back to the first control chip 21 through the startup circuit 3. At the same time, the first power inductor 23 stops oscillating, causing the auxiliary power supply circuit 4 to lose the maintaining voltage, and the power supply of the first control chip 21 smoothly returns to zero as the energy storage capacitor discharges naturally. The dual mechanisms ensure that the subsequent driving circuit is completely turned off, avoiding the intermittent restart of the LED lamp beads caused by the slow release of the capacitor energy.

[0027] Preferably, the startup circuit 3 further includes a first diode, a first voltage-dividing resistor group, and a second voltage-dividing resistor group. The negative voltage shutdown device 31 is a depletion-type NMOS transistor, and the first diode is a zener diode; The drain of the negative voltage shutdown device 31 is connected to the output terminal of the power supply module 1 through the first voltage-dividing resistor group, the gate is connected to the output terminal of the power supply module 1 through the second voltage-dividing resistor group, and the source is connected to the power supply terminal of the first control chip 21; The gate of the negative voltage shutdown device 31 is also connected to the cathode of the first diode, and the anode of the first diode is grounded.

[0028] See Figure 1 and Figure 2, in a specific embodiment of the present invention, the startup circuit 3 further includes a first diode DZ1, a first voltage dividing resistor group, and a second voltage dividing resistor group. The negative voltage shutdown device 31 is a depletion-type NMOS transistor Q2, and the first diode DZ1 is a 10V zener diode. In this embodiment, the first voltage dividing resistor group includes resistor R9 and resistor R10, and the second voltage dividing resistor group includes resistor R12 and resistor R13. The drain of the negative voltage shutdown device 31 is connected to the bus voltage output terminal of the power supply module 1 through the series connection of resistor R9 and R10. The gate of the negative voltage shutdown device 31 is connected to the bus voltage output terminal through the series connection of resistor R12 and R13. The source of the negative voltage shutdown device 31 is directly connected to the VCC pin of the first control chip 21. The cathode of the zener diode DZ1 is connected to the gate of the negative voltage shutdown device 31, and the anode is grounded, which is used to clamp the gate voltage. When power is initially applied, the bus voltage of the power supply module 1 is divided by the first voltage dividing resistor group and the second voltage dividing resistor group, so that the gate voltage of the negative voltage shutdown device 31 is limited within 10V by the first diode DZ1, avoiding overvoltage breakdown, and at the same time ensuring that the negative voltage shutdown device 31 stably supplies power to the VCC pin of U1 in the conducting state. After the auxiliary power supply circuit 4 is started, the source voltage of the negative voltage shutdown device 31 rises, the gate is clamped at 10V due to the first diode DZ1, and the gate-source voltage difference becomes negative, triggering the negative voltage shutdown device 31 to turn off, and the startup circuit 3 completely exits.

[0029] It can be understood that in this embodiment, through the voltage division of resistor R12 and resistor R13 in the second voltage dividing resistor group and the voltage stabilization clamping of the first diode DZ1, it is ensured that the gate voltage of the negative voltage shutdown device 31 is always lower than its withstand voltage limit, avoiding device damage in the high-voltage input scenario, and at the same time accurately setting the shutdown threshold to ensure the reliability of negative voltage triggering. Secondly, resistor R9 and resistor R10 in the first voltage dividing resistor group can adopt small resistance values to reduce the voltage drop from the bus voltage to the VCC pin, reduce the resistance loss in the startup stage, and improve the power utilization rate. The clamping effect of the first diode DZ1 and the collaborative design of the voltage dividing resistors make the negative voltage shutdown device 31 completely turn off during the operation stage, avoiding the leakage of the bus voltage to the VCC pin through the voltage dividing resistors, thereby further reducing the standby power consumption. Those skilled in the art can make corresponding equivalent improvements according to the application scenario based on the collaborative design of negative voltage shutdown and voltage dividing resistors of the present invention. For example: replacing the resistor with a variable resistor, a multi-stage series resistor or an integrated resistor network, adjusting the resistance ratio to adapt to different bus voltage ranges, while maintaining precise control of the gate voltage; using a combination of TVS tubes or zener diodes to replace the zener diode DZ1 to achieve overvoltage protection and voltage clamping functions in the gate path to prevent high-voltage breakdown.

[0030] It should be noted that, in addition to the depletion-type NMOS tube Q2, the negative voltage shutdown device 31 may also select other semiconductor devices with negative voltage shutdown characteristics, for example: using an N-channel junction field effect tube (JFET, such as model J175) to replace the depletion-type NMOS tube Q2, the JFET is naturally turned on at zero gate voltage, and the drain-source is directly turned on to power the first control chip 21 when initially powered on. When the auxiliary power supply circuit 4 is started, the source voltage increases, and the gate-source is reversely biased through the voltage divider resistor group and the voltage regulator tube, triggering the pinch-off effect to achieve shutdown; or using an enhanced NMOS tube in combination with an external bias resistor network, when initially powered on, a positive voltage is provided to the gate through a resistor voltage divider, forcing the MOS tube to be turned on, and after the auxiliary power supply circuit 4 is started, the source voltage increases, and the divider resistor group cooperates with the voltage regulator tube to form a reverse bias, triggering the pinch-off effect, and achieving shutdown; or using an enhanced NMOS tube in combination with an external bias resistor network, when initially powered on, a positive voltage is provided to the gate through a resistor voltage divider, forcing the MOS tube to be turned on, and after the auxiliary power supply circuit 4 is started, the source voltage increases, and the divider resistor group cooperates with the voltage regulator tube to form a reverse bias, triggering the pinch-off effect, and achieving shutdown; The voltage network makes the gate-source voltage lower than the threshold value, and the MOS tube is turned off. It is necessary to add resistors and voltage regulator tubes to ensure the stability of the bias voltage; or an optocoupler (such as model PC817) is used as the core, and a discrete MOS tube is used. When the power is initially turned on, the bus voltage triggers the phototransistor to turn on through the internal LED of the optocoupler, and drives the external MOS tube to power the first control chip 21. After the auxiliary power supply circuit 4 is started, the input side of the optocoupler is pulled down by the auxiliary voltage, the phototransistor is turned off, and the power supply path is cut off. It is necessary to add a current limiting resistor and a reverse protection diode; or an IGBT is used with a voltage comparator, and the voltage detection chip monitors the output voltage of the auxiliary power supply circuit 4 in real time. When the voltage reaches the threshold, a low-level signal is output to drive the IGBT to turn off. The initial conduction is achieved by the parasitic diode or pre-charge resistor of the IGBT. Although the above schemes have different device types or driving logics, they can all achieve the core advantages of fast startup, low loss during operation, and no flashback during power failure. No external driving signal is required, and the power supply path is automatically established when power is turned on. After the auxiliary power supply is started, the shutdown condition is formed through device characteristics or external circuits. After power failure, the bus residual voltage backflow path is completely blocked to prevent false triggering. It is an equivalent deformation of the technical personnel in this field based on the principle of the present invention.

[0031] Preferably, the rectifier and filter circuit 42 includes a second diode, a third diode and a first resistor; the second diode is a voltage regulator diode, and the voltage regulation value of the second diode is greater than the voltage regulation value of the first diode; the first end of the first auxiliary winding 41 is connected to one end of the first resistor, and the other end of the first resistor is connected to the anode of the third diode, the cathode of the third diode and the cathode of the second diode are connected to the power supply end of the first control chip 21, and the anode of the second diode is grounded.

[0032] See also Figure 1 and Figure 3, in a specific embodiment of the present invention, the rectifier filter circuit 42 includes a second diode DZ2, a third diode D7, and a first resistor R14; in this embodiment, the second diode DZ2 is an 18V zener diode, and the third diode D7 is a fast recovery diode; the first end of the first auxiliary winding 41 is connected to one end of the first resistor R14, the other end of the first resistor R14 is connected to the anode of the third diode D7, the cathode of the third diode D7 and the cathode of the second diode DZ2 are commonly connected to the power supply terminal VCC pin of the first control chip 21, and the anode of the second diode DZ2 is grounded. The working process is as follows: in the initial power-on stage, the positive half-cycle signal of the alternating voltage is induced by the first auxiliary winding 41, and after being limited by the first resistor R14, it is unidirectionally conducted by the third diode D7 to supply power to the power supply terminal VCC pin of the first control chip 21. When the VCC voltage rises to the 18V zener voltage value of the second diode DZ2, DZ2 is reversely broken down, and the voltage is clamped at 18V; in the operation stage, the second diode DZ2 stabilizes the voltage of the VCC pin of the first control chip 21 at 18V. At the same time, the gate of the negative voltage turn-off device 31 is maintained at 10V due to the clamping effect of the first diode DZ1, resulting in a negative voltage difference of -8V between the gate and the source (Vgs = 10V - 18V = -8V), thereby triggering the negative voltage turn-off device 31 to completely turn off. At this time, the power supply is completely maintained by the auxiliary winding 41 through the third diode D7 and the first resistor R14; in the power-off stage, after the bus voltage disappears, the auxiliary winding 41 stops oscillating, and the third diode D7 is cut off due to no input signal. At this time, the voltage of the VCC pin of the first control chip 21 is maintained by the energy storage capacitor (such as capacitors EC2 and C2) and gradually decreases as the capacitor discharges. Since the negative voltage turn-off device 31 is already in the off state, the power supply path of the starting circuit 3 is completely blocked, and the VCC pin voltage cannot be re-established by the residual bus voltage or the starting circuit. As the capacitor energy continues to be released, the VCC pin voltage smoothly drops to zero, and the drive circuit is completely turned off, avoiding the LED lamp beads from flashing back due to voltage fluctuations.

[0033] It can be understood that in this embodiment, through the coordinated voltage stabilization of the second diode DZ2 and the first diode DZ1, the 18V voltage stabilization value of the second diode DZ2 is higher than the 10V voltage stabilization value of the first diode DZ1 in the startup circuit. Under the dual clamping, it not only ensures that a stable negative voltage difference (-8V) is formed between the gate and source of the voltage-off device 31 to trigger its reliable turn-off, but also avoids overvoltage damage to the control chip caused by the overshoot of the auxiliary power supply voltage. At the same time, the third diode D7 uses a fast-recovery diode, which can significantly reduce the reverse recovery loss during rectification. Combining with the current-limiting effect of the first resistor R14, the energy conversion efficiency of the auxiliary winding 41 can be improved. After power-off, the auxiliary winding 41 stops oscillating, causing the third diode D7 to cut off. The voltage of the VCC pin is maintained by the energy storage capacitor and smoothly drops with discharge. Cooperating with the physical isolation of the negative voltage-off device 31, the reverse injection path of the residual voltage on the bus is completely blocked, eliminating the backflash phenomenon of the LED beads caused by voltage fluctuations. Based on the voltage stabilization coordinated control and rectification and filtering integrated design of the present invention, those skilled in the art can make corresponding equivalent improvements according to the application scenario. For example, the third diode D7 can be replaced with a Schottky diode (such as 1N5817) to further reduce the conduction voltage drop, or an ultrafast-recovery diode (such as UF4007) can be used to improve the high-frequency response speed; or according to the withstand voltage range of the control chip, the voltage stabilization value of the second diode DZ2 can be adjusted to 15V or 20V, and the voltage stabilization value of the first diode DZ1 can be synchronously adjusted to 8V or 12V, maintaining the difference (such as 7-8V) that the voltage stabilization value of the second diode DZ2 is always higher than that of the first diode DZ1 to ensure the reliable triggering of the negative voltage-off device 31; or the first resistor R14 can be replaced with a variable resistor or a parallel structure of multiple resistors to dynamically adapt to the output voltage range of different auxiliary windings 41 and optimize the current-limiting intensity; or a transient voltage suppression diode TVS can be used to replace the second diode DZ2 to enhance the transient overvoltage protection ability of the VCC pin while realizing the voltage stabilization function. For example, an SMBJ18A model TVS tube can be selected.

[0034] Preferably, the energy conversion module includes an auxiliary winding 41 magnetically coupled to the main winding of the first power inductor 23, and a rectification and filtering circuit 42 connected to the auxiliary winding 41.

[0035] See Figure 1 and Figure 3, in a specific embodiment of the present invention, the energy conversion module of the auxiliary power supply circuit includes a first auxiliary winding 41 and a rectifying and filtering circuit 42; the first auxiliary winding 41 is magnetically coupled to the main winding of the first power inductor 23, the input end of the rectifying and filtering circuit 42 is connected to the first auxiliary winding 41, and the output end is connected to the power supply end of the first control chip 21. The auxiliary winding 41 and the main winding of the first power inductor 23 can be magnetically coupled through the same magnetic core or different magnetic cores: when using the same magnetic core, the auxiliary winding 41 and the main winding are wound on the same magnetic core with a specific turns ratio, and energy transfer is directly realized through magnetic field alternation, with a compact structure and high coupling efficiency; if different magnetic cores are used, the main winding and the auxiliary winding 41 are respectively wound on independent magnetic cores, and a coupling path is formed through magnetic circuit design, for example, the coupling intensity is adjusted by preset air gaps or magnetic shielding layers between the magnetic cores. This solution can adapt to different space layout requirements and reduce the risk of magnetic saturation. Regardless of the magnetic core configuration used, the alternating magnetic field generated by the main winding under the drive of the first field effect control switch tube 22 will induce an alternating voltage in the auxiliary winding 41, which is converted into a stable DC voltage by the rectifying and filtering circuit 42 to continuously supply power to the control chip 21.

[0036] It can be understood that through the magnetic coupling design of the auxiliary winding 41 and the main winding and the synergistic effect of the rectifying and filtering circuit 42, the present invention improves the efficiency of energy conversion and the stability of power supply. When the auxiliary winding 41 and the main winding use the same magnetic core, the structure is compact and the magnetic field alternation directly transfers energy, significantly improving the coupling efficiency and ensuring that the control chip quickly obtains a stable DC voltage; when using independent magnetic cores, different space layout requirements can be flexibly adapted through magnetic circuit optimization, reducing the risk of magnetic saturation and enhancing the reliability of the system; the rectifying and filtering circuit 42 efficiently converts the induced alternating voltage into a DC power supply to continuously supply power to the main control chip 21. Its low-loss characteristics during the operation stage and the coordinated control mechanism of the main winding stopping oscillation when power is off completely block the reverse flow path of the residual voltage on the bus. Combined with the smooth discharge of the energy storage capacitor, it ensures that the LED load instantaneously extinguishes without backflash. The overall solution combines structural flexibility, high energy conversion efficiency, and operation stability.

[0037] Based on the above magnetic coupling principle, those skilled in the art can further achieve auxiliary power supply through other energy coupling methods. For example, when using capacitive coupling, the voltage fluctuation of the main winding is transmitted to the energy conversion module through the coupling capacitor and is rectified and filtered to supply power to the control chip; or when using a direct electrical connection method, a partial voltage signal is directly extracted from the main winding through a resistor voltage division network or an inductive tap, and then a DC power supply is generated through a conversion circuit. Although the above alternative solutions have different energy transfer paths, they can all generate an auxiliary power supply voltage when the main winding is working, and through the synergistic effect of the negative voltage turn-off device and the main winding stopping oscillation when power is off, the complete blocking of the residual voltage on the bus and the rapid turn-off of the power supply circuit are realized, thus ensuring the non-backflash extinguishing of the LED load, which belongs to the equivalent deformation of the technical concept of the present invention.

[0038] Preferably, the rectifying and filtering circuit 42 further includes a fourth diode and a first capacitor; a first end of the first auxiliary winding 41 is connected to one end of a first resistor through the first capacitor, a second end of the first auxiliary winding 41 and an anode of the fourth diode are commonly connected to ground, and a cathode of the fourth diode is connected to the other end of the first resistor.

[0039] See Figure 1 and Figure 3 , in a specific embodiment of the present invention, the rectifying and filtering circuit 42 further includes a fourth diode D8 and a first capacitor C10. A first end of the first auxiliary winding 41 is connected to one end of a first resistor R14 through the first capacitor C10, a second end of the first auxiliary winding 41 and an anode of the fourth diode D8 are commonly connected to ground, and a cathode of D8 is connected to the other end of the first resistor R14. A cathode of the second diode DZ2 and a cathode of the third diode D7 are commonly connected to a VCC pin of the first control chip 21, and an anode of the second diode DZ2 is grounded. The working process is as follows: In the initial power-on stage, a positive half-cycle of an AC signal of the first auxiliary winding 41 is coupled to the first resistor R14 through the first capacitor C10, rectified by the third diode D7 and then charges the VCC pin of the first control chip 21, and a negative half-cycle forms a freewheeling path through the fourth diode D8 to avoid reverse breakdown of the winding voltage; in the operation stage, the first capacitor C10 and the first resistor R14 form an RC coupling network to filter out high-frequency switching noise. At the same time, the cooperative rectification of the third diode D7 and the fourth diode D8 converts the AC signal of the auxiliary winding 41 into DC, and after being regulated by the second diode DZ2, a stable voltage of 18V is output. At this time, the negative voltage turn-off device 31 is turned off due to an 8V voltage difference between the gate and the source, and the power supply is completely maintained by the auxiliary winding 41; in the power-off stage, after the bus voltage of the power supply module 1 disappears, the auxiliary winding 41 stops oscillating, the first capacitor C10 stops coupling due to no AC input, the third diode D7 and the fourth diode D8 are cut off, and the voltage of the VCC pin of the first control chip 21 slowly drops to zero by the energy storage capacitors (such as capacitors EC2 and C2), without residual energy triggering flashback.

[0040] It can be understood that in this embodiment, a voltage doubler rectifier structure is formed by the first capacitor C10, the third diode D7, and the fourth diode D8. By utilizing the positive and negative half-cycle energy of the auxiliary winding 41, the voltage of the VCC pin can reach 18V faster, effectively shortening the startup time. An RC network is formed by the first capacitor C10 and the first resistor R14 to effectively filter out the high-frequency ripple generated by the switching action of the first field-effect control switch tube 22, improving the purity of the VCC voltage. The fourth diode D8 provides a low-impedance path for the negative half-cycle of the auxiliary winding 41, avoiding energy loss caused by the accumulation of reverse voltage and protecting the winding insulation at the same time. Those skilled in the art can make corresponding equivalent improvements according to the application scenario. For example, the third diode D7 and the fourth diode D8 can be replaced with a dual-diode integrated package device (such as BAS316TW) to reduce the layout space and welding points and improve reliability; or a silicon carbide diode (such as C3D02060) can be used to improve the rectification efficiency under high-temperature conditions; or a transient voltage suppressor TVS can be connected in parallel across the second diode DZ2 to form a double overvoltage protection. For example, a TVS tube of the SMBJ18CA model is selected and connected in parallel with an 18V voltage regulator tube to enhance the ability to suppress surge voltage; or the first resistor R14 can be replaced with a negative temperature coefficient thermistor NTC to reduce the resistance at low-temperature startup to accelerate power supply establishment and increase the resistance during high-temperature operation to limit the current, adapting to the requirements of a wide-temperature environment; or the first capacitor C10 can be removed and a current transformer is added between the auxiliary winding 41 and the first resistor R14 to transmit energy through magnetic coupling and reduce high-frequency noise interference.

[0041] Preferably, the rectifier filter circuit 42 further includes a second capacitor and a third capacitor, and the second capacitor and the third capacitor are connected in parallel between the power supply terminal of the first control chip 21 and the ground.

[0042] See Figure 1 and Figure 3, in a specific embodiment of the present invention, the rectifier filter circuit 42 further includes a second capacitor C2 and a third capacitor EC2; in this embodiment, the second capacitor C2 is a chip X7R capacitor, and the third capacitor EC2 is an electrolytic capacitor; the second capacitor C2 and the third capacitor EC2 are connected in parallel between the power supply terminal VCC pin of the first control chip 21 and the ground; the first end of the first auxiliary winding 41 is connected to one end of the first resistor R14 through the first capacitor C10, the second end of the first auxiliary winding 41 and the anode of the fourth diode D8 are commonly connected to the ground, and the cathode of the fourth diode D8 is connected to the other end of the first resistor R14. The cathode of the third diode D7 and the cathode of the second diode DZ2 are commonly connected to the VCC pin of the first control chip 21, and the anode of the second diode DZ2 is grounded. The working process is as follows: In the initial power-on stage, the AC voltage of the auxiliary winding 41 is coupled through the first capacitor C10, limited by the first resistor R14, and rectified by the third diode D7, and then charges the second capacitor C2 and the third capacitor EC2 connected in parallel. The second capacitor C2 quickly responds to high-frequency components to suppress transient voltage fluctuations, and the EC2 stores the main energy to provide a stable DC voltage; in the operation stage, the second capacitor C2 filters out the high-frequency switching noise at the power supply terminal VCC pin of the first control chip 21 (such as the ripple caused by the switching of the first field-effect control switch tube 22), and the third capacitor EC2 smooths the low-frequency voltage fluctuations. The two work together to ensure that the VCC voltage is stable at 18V and is accurately clamped through the second diode DZ2; in the power-off stage, after the bus voltage of the power module 1 disappears, the auxiliary winding 41 stops oscillating, the third diode D7 and the fourth diode D8 are cut off, and the electric energy stored in the third capacitor EC2 is slowly released through the internal circuit of the first control chip 21. The second capacitor C2 quickly discharges the high-frequency residual charge, and the power supply terminal VCC voltage of the first control chip 21 smoothly drops to zero, avoiding flashback.

[0043] It can be understood that the second capacitor C2 and the third capacitor EC2 are connected in parallel to form a broadband filter network, which respectively suppresses high-frequency noise and low-frequency ripple, and can improve the stability of the VCC voltage; the fast charge and discharge characteristics of the second capacitor C2 ensure the immediate suppression of switching noise, and the large-capacity energy storage of the third capacitor EC2 maintains the slow-drop curve of the VCC voltage after power-off. The dual mechanism eliminates the risk of flashback; the combination of low-cost electrolytic capacitors and chip capacitors can achieve efficient filtering in a limited space, taking into account the circuit reliability and economy. Those skilled in the art can make corresponding equivalent improvements according to the application scenario. For example: replacing the second capacitor C2 with a thin-film capacitor to improve the high-frequency characteristics, or replacing the third capacitor EC2 with a tantalum capacitor to reduce the volume; or adjusting the capacitance of the second capacitor C2 and the third capacitor EC2 according to the load current size to adapt to different filtering requirements; or connecting a small-value resistor in series between C2 and EC2 to form an RC filter network to enhance the high-frequency attenuation effect; or replacing C2 with multiple parallel chip capacitors to disperse the equivalent series resistance and further reduce the high-frequency impedance.

[0044] Preferably, the drive control circuit 2 further includes a fifth diode, and the first field effect control switch tube 22 is an enhancement-mode NMOS tube; the drain of the first field effect control switch tube 22 is connected to the output end of the power supply module 1, the gate is connected to the drive end of the first control chip 21, and the source is commonly connected to the input end of the main winding of the first power inductor 23 with the cathode of the fifth diode, and the anode of the fifth diode is grounded.

[0045] See Figure 1 and Figure 4 , in a specific embodiment of the present invention, the drive control circuit 2 includes a fifth diode D5, a first field effect control switch tube 22 (enhancement-mode NMOS tube Q1) and the main winding of the first power inductor 23. The drain of the first field effect control switch tube 22 is connected to the bus voltage output end of the power supply module 1, the gate is connected to the drive end Gate pin of the first control chip 21, the source is commonly connected to the input end of the main winding with the cathode of D5, and the anode of the fifth diode D5 is grounded. The output end of the main winding is connected to the positive pole of the LED load, and the negative pole of the LED load is grounded. The working process is as follows: in the conduction stage, the first control chip 21 outputs a high-level drive signal, so that the first field effect control switch tube 22 is turned on, and the bus voltage charges the main winding through the drain-source of the first field effect control switch tube 22 (enhancement-mode NMOS tube Q1), the inductor stores energy, and the LED load lights up; in the off stage, the drive signal output by the first control chip 21 becomes low level, so that the first field effect control switch tube 22 is turned off, the main winding generates a reverse electromotive force, forms a freewheeling path through the fifth diode D5, releases the inductor energy, and maintains the continuity of the LED current. At the moment when the first field effect control switch tube 22 is turned off, the drain voltage generates a spike due to the sudden change of the inductor current. The fast conduction characteristic of the fifth diode D5 clamps the spike voltage within a safe range (Vds≈bus voltage + 0.7V), avoiding breakdown of the first field effect control switch tube 22 (enhancement-mode NMOS tube Q1).

[0046] It is understandable that through the collaborative design of introducing the fifth diode D5 and the first field-effect control switch tube 22 (enhanced NMOS tube Q1), efficient and reliable LED drive control is achieved in the BUCK topology. The specific advantages are as follows: The fifth diode D5 provides a low-impedance freewheeling path during the inductor turn-off stage, avoiding relying on the body diode of the first field-effect control switch tube 22, significantly reducing switching losses, and at the same time suppressing the voltage spike caused by the inductor back electromotive force to protect the first field-effect control switch tube 22 to work safely; The fast-recovery characteristic of the fifth diode ensures that the inductor energy is continuously released through the LED load, maintaining low ripple of the LED current and avoiding visible stroboscopic; The simple combination of a single diode and a switch tube does not require a complex drive circuit, significantly reducing the component cost and layout area compared with the synchronous rectification scheme; The freewheeling effect of the fifth diode D5 enables the inductor energy to be quickly released after power-off. Combined with the negative voltage turn-off design, it ensures that the residual voltage on the bus cannot re-establish power supply, eliminating the risk of backflash. Those skilled in the art can make corresponding equivalent improvements according to the application scenario. For example: replacing the fifth diode D5 with a Schottky diode to reduce the freewheeling voltage drop, such as using the BAT54S model, which is suitable for high-current scenarios; or using an ultra-fast recovery diode such as ES1D to adapt to high-frequency switching requirements and improve the reverse recovery speed; or using synchronous rectification technology, replacing the fifth diode D5 with an external MOS tube and driving it complementarily with the first field-effect control switch tube 22, and realizing high-efficiency freewheeling through the control chip output synchronous signal, but a dead-time control logic needs to be added; or directly relying on the parasitic body diode of the enhanced NMOS tube for freewheeling, omitting the external diode to simplify the circuit, which is suitable for low-frequency and low-power scenarios; or integrating the switch tube and the freewheeling diode into a single power module package, such as the FDMC8622 model, reducing parasitic inductance and optimizing the high-frequency response characteristics. The above schemes are all based on the core structure of the switch tube-inductor-freewheeling path of the BUCK topology, and can be equivalently adjusted according to the requirements of efficiency, cost or application scenario under the premise of maintaining the anti-backflash and dynamic power supply switching mechanisms.

[0047] Preferably, the drive control circuit 2 further includes a sixth diode, a second resistor, a third resistor and a fourth resistor; The anode of the sixth diode, one end of the second resistor, and one end of the third resistor are commonly connected to the gate of the first field-effect control switch tube 22, and the other end of the second resistor is connected to the source of the first field-effect control switch tube 22; The cathode of the sixth diode is connected to one end of the fourth resistor, and the other end of the third resistor and the other end of the fourth resistor are commonly connected to the drive end of the first control chip 21.

[0048] See Figure 1 and Figure 4, in a specific embodiment of the present invention, the drive control circuit 2 includes a sixth diode D9, a second resistor R8, a third resistor R7, and a fourth resistor R38; in this embodiment, the sixth diode D9 is a Schottky diode; the anode of the sixth diode D9, one end of the second resistor R8, and one end of the third resistor R7 are commonly connected to the gate of the first field effect control switch tube 22, and the other end of the second resistor R8 is connected to the source of the first field effect control switch tube 22; the cathode of the sixth diode D9 is connected to one end of the fourth resistor R38, and the other end of the third resistor R7 and the other end of the fourth resistor R38 are commonly connected to the drive end Gate pin of the first control chip 21. The working process is as follows: In the conduction stage, the first control chip 21 outputs a high-level drive signal, which charges the gate of the first field effect control switch tube 22 after being divided by the third resistor R7 and the fourth resistor R38. At this time, the sixth diode D9 is reversely cut off because the cathode potential is higher than the anode, and the charging current is dominated by the third resistor R7 path, and the second resistor R8 limits the peak current; in the turn-off stage, the drive signal output by the first control chip 21 jumps to a low level, and the gate charge of the first field effect control switch tube 22 forms a low-impedance discharge path through the forward conduction of the sixth diode D9, and at the same time, the energy is slowly released through the second resistor R8 and the third resistor R7 to suppress the drain voltage spike; the Schottky characteristic of the sixth diode D9 limits its forward voltage drop within 0.3V, accelerates the turn-off process and naturally clamps the gate negative voltage to prevent electrostatic breakdown.

[0049] It can be understood that in this embodiment, through the cooperative action of the asymmetric conduction characteristic of the sixth diode D9 and the resistor network, rapid charging and controllable turn-off of the gate drive are achieved; the low conduction voltage drop and fast recovery characteristic of the Schottky diode reduce the switching loss, and cooperate with the resistor network to suppress voltage oscillation and EMI noise; the integrated design completes drive optimization and electrostatic protection in a single loop without additional components. Those skilled in the art can adopt the following equivalent adjustments: replace the sixth diode D9 with an ultra-fast recovery diode to adapt to high-frequency scenarios; adjust the resistance ratio of the third resistor R7 and the fourth resistor R38 to match the gate charge requirements of different MOS tubes; remove the second resistor R8 and connect a ferrite bead in series at the gate to suppress high-frequency oscillation; use an integrated gate drive chip to replace the discrete resistor and diode network; replace the sixth diode D9 and the resistor network with an RC buffer circuit to absorb high-frequency noise.

[0050] Preferably, the drive control circuit 2 further includes a voltage sampling circuit 24 and a current sampling circuit 25; the voltage sampling circuit 24 includes a third voltage dividing resistor group and a fourth capacitor; the third voltage dividing resistor group is connected across the output terminal of the main winding of the first power inductor 23 and the ground; the voltage feedback terminal of the first control chip 21 is connected to the sampling node of the third voltage dividing resistor group and grounded through the fourth capacitor; the current sampling circuit 25 includes a fifth capacitor and a sixth resistor; one end of the sixth resistor is connected to the source of the first field effect control switch tube 22, and the other end is commonly connected to the current feedback terminal of the first control chip 21 with one end of the fifth capacitor, and the other end of the fifth capacitor is grounded.

[0051] See Figure 1 and Figure 4 In a specific embodiment of the present invention, the drive control circuit 2 includes a voltage sampling circuit 24 and a current sampling circuit 25; the voltage sampling circuit 24 is composed of a third voltage dividing resistor group and a fourth capacitor C1. The third voltage dividing resistor group includes resistors R15, R16, R17, and R18 connected in series, and is connected across the output terminal of the main winding of the first power inductor 23 and the ground; the voltage feedback terminal FB pin of the first control chip 21 is connected to the sampling node between resistor R16 and R17 and grounded through the fourth capacitor C1. The current sampling circuit 25 includes a fifth capacitor C3 and a sixth resistor R6. One end of the sixth resistor R6 is connected to the source of the first field effect control switch tube 22, and the other end is commonly connected to the current feedback terminal CS pin of the first control chip 21 with one end of the fifth capacitor C6, and the other end of the fifth capacitor C3 is grounded. The working process is as follows: After the output voltage of the LED load is divided by the series resistors R15 to R18, a feedback voltage signal is generated at the node between resistor R16 and R17. After filtering out high-frequency switching noise through the fourth capacitor C1, the smoothed signal is input to the voltage feedback terminal FB pin of the first control chip 21. The first control chip 21 dynamically adjusts the duty cycle through an internal error amplifier to achieve constant voltage output; when the first field effect control switch tube 22 is turned on, the source current flows through the sixth resistor R6 to generate a sampling voltage. After the fifth capacitor C3 filters out the high-frequency spikes in the current signal, it is input to the current feedback terminal CS pin of the first control chip 21. The first control chip 21 limits the peak current in real time through an internal comparator to achieve constant current control.

[0052] It can be understood that in this embodiment, through the collaborative design of the voltage sampling circuit and the current sampling circuit, high-precision closed-loop control of the LED load voltage and current is achieved; the voltage sampling circuit uses a voltage-dividing resistor group connected across the inductor output terminal and the ground, and feeds back the voltage signal to the control chip through the voltage-dividing node, combined with a filtering capacitor to suppress high-frequency noise, ensuring the stability of the constant voltage output; the current sampling circuit uses a combination of a source series resistor and a filtering capacitor to accurately capture the switch tube current signal to achieve constant current control; the flexible configuration of the voltage-dividing resistor group can adapt to different LED voltage ranges, and the selection of the filtering capacitor takes into account anti-interference and response speed. The overall solution simplifies the design while ensuring output accuracy and reliability. Those skilled in the art can adjust the number of resistors and the resistance ratio of the voltage-dividing resistor group based on application requirements. For example, using two resistors for voltage division to simplify the circuit or increasing the number of resistors to improve voltage division accuracy; replacing the voltage-dividing resistor group with a digital potentiometer or an integrated voltage sensor to dynamically calibrate the feedback voltage through a digital signal; the sixth resistor in the current sampling circuit can be replaced with a current transformer or a Hall sensor to achieve non-contact current detection to reduce power consumption; the filtering capacitor can use a π-type network or multi-stage filtering to enhance noise suppression; a voltage stabilizing diode can be added to the voltage-dividing node to limit voltage overshoot and prevent the control chip from being damaged under abnormal conditions. The core of this embodiment is to achieve constant voltage and constant current control of LED driving through the collaborative feedback of the voltage-dividing resistor group and the source sampling resistor. The number of voltage-dividing resistors and the specific resistance ratio can be flexibly adjusted according to actual needs. The above adjustments all retain the core mechanism of voltage-current feedback and belong to the equivalent deformation within the scope of this patent protection.

[0053] Preferably, the anti-backflash LED driving circuit further includes a boost circuit 5. The boost circuit 5 includes a second control chip, a second power inductor, a seventh diode, a second field effect control switch tube, and a sixth capacitor; the first input terminal of the second control chip is connected to the output terminal of the power supply module 1, the second input terminal is connected to the first end of the auxiliary winding of the second power inductor, and the driving terminal is connected to the gate of the second field effect control switch tube; the second end of the auxiliary winding of the second power inductor is grounded; the first end of the main winding of the second power inductor is connected to the output terminal of the power supply module 1, the second end is connected to the drain of the second field effect control switch tube and the anode of the seventh diode, the cathode of the seventh diode is connected to the positive electrode of the sixth capacitor, the source of the second field effect control switch tube is grounded, and the negative electrode of the sixth capacitor is grounded.

[0054] See Figure 1 and Figure 5, in a specific embodiment of the present invention, the boost circuit 5 includes a second control chip U2, a second power inductor T2, a seventh diode D6, a second field effect control switch Q3, and a sixth capacitor EC1; the HV pin of the second control chip U2 is connected to the bus voltage output terminal of the power supply module 1, the VCC pin is connected to the first end of the auxiliary winding of the second power inductor T2, and the drive end GATE pin is connected to the gate of the second field effect control switch Q3; the second end of the auxiliary winding of the second power inductor T2 is grounded; the first end of the main winding of the second power inductor T2 is connected to the bus voltage output terminal of the power supply module 1, the second end is connected to the drain of the second field effect control switch Q3 and the anode of the seventh diode D6, and the source of the second field effect control switch Q3 is grounded; the cathode of the seventh diode D6 is connected to the positive electrode of the sixth capacitor EC1, and the negative electrode of the sixth capacitor EC1 is grounded; the positive electrode of the sixth capacitor EC1 serves as the output terminal of the boost circuit 5 at the same time. The working process is as follows: in the initial power supply stage, the bus voltage output by the power supply module 1 supplies power to the second control chip U2 through the HV pin, and at the same time provides input energy for the boost circuit through the first end of the main winding of the second power inductor T2; in the conduction stage, the second control chip U2 outputs a high-level drive signal through the GATE pin to turn on the second field effect control switch Q3, so that the main winding of the inductor T2 stores energy; in the off stage, the drive signal of the second control chip U2 jumps to a low level to turn off the second field effect control switch Q3, and the main winding of the inductor T2 generates a reverse electromotive force, and the inductor energy charges the sixth capacitor EC1, causing the voltage at the boost output terminal to increase; the induced voltage of the auxiliary winding of the second power inductor T2 provides a working power supply for the second control chip U2 through the VCC pin, and at the same time is fed back to the adjustment module of the second control chip U2 after being processed by the internal circuit to dynamically adjust the duty cycle of the second field effect control switch Q3 to maintain the stability of the boost output voltage.

[0055] It can be understood that the boost circuit in this embodiment effectively solves the stability problem in the wide input voltage scenario through a closed-loop control mechanism. Whether the input voltage is too high or too low, the second control chip dynamically adjusts the duty cycle of the second field-effect control switch tube to ensure that the boost output is stably maintained at 400V, adapting to the driving requirements of high-voltage LED lamp strings; the seventh diode D6 and the sixth capacitor EC1 cooperate to achieve efficient energy conversion, and the conversion efficiency remains above 90% even when the input voltage fluctuates, reducing energy loss; the feedback signal of the auxiliary winding of the second power inductor T2 directly participates in voltage regulation, correcting the output deviation in real time and enhancing the anti-interference ability of the system. In addition, the boost output terminal is coupled with the drive control circuit. After power-off, the energy stored in the sixth capacitor EC1 is quickly released through the discharge resistor, avoiding the LED beads from flashing back due to the residual voltage and achieving flicker-free turn-off. Those skilled in the art can adjust according to actual needs: use SEPIC or buck-boost topology to replace the basic boost topology to further expand the input voltage range; or replace the second control chip U2 with a digital control type IC to optimize the dynamic response accuracy through software algorithms; or add an active discharge circuit at the output terminal to control the energy discharge speed with a transistor to adapt to different capacitance values; or select gallium nitride devices to replace traditional MOS tubes to improve the high-frequency switching performance and reduce losses. The above improvements can flexibly adapt to the scenario requirements such as high efficiency, high precision, or ultra-wide input voltage while maintaining the core functions of wide voltage adaptation and anti-backflash.

[0056] Preferably, the boost circuit 5 further includes a seventh resistor, an eighth resistor, a seventh capacitor, and an eighth diode; one end of the seventh capacitor is connected to the first end of the auxiliary winding of the second power inductor, and the other end is connected to one end of the seventh resistor and one end of the eighth resistor; the other ends of the seventh resistor and the eighth resistor are commonly connected to the anode of the eighth diode, and the cathode of the eighth diode is connected to the second input terminal of the second control chip.

[0057] See Figure 1 and Figure 5, in a specific embodiment of the present invention, the boost circuit 5 further includes a seventh resistor R2, an eighth resistor R11, a seventh capacitor C7, and an eighth diode D3; one end of the seventh capacitor C7 is connected to the first end of the auxiliary winding of the second power inductor T2, and the other end is connected to one end of the seventh resistor R2 and one end of the eighth resistor R11; the other ends of the seventh resistor R2 and the eighth resistor R11 are commonly connected to the anode of the eighth diode D3, and the cathode of the eighth diode D3 is connected to the second input terminal VCC pin of the second control chip U2. The working process is as follows: In the startup stage, when initially powered on, the bus voltage of the power supply module 1 injects a tiny startup current into the second control chip U2 through the HV pin, triggering the internal logic of the chip to start working. At this time, the second control chip U2 drives the second field-effect control switch tube Q3 to conduct for the first time through the GATE pin, and the main winding of the second power inductor T2 starts to store energy; in the power supply maintenance stage, after the second field-effect control switch tube Q3 is turned off for the first time, an alternating voltage is induced in the auxiliary winding of the second power inductor T2. The positive half-cycle signal of it is coupled to the voltage dividing network composed of the seventh capacitor C7, the seventh resistor R2, and the eighth resistor R11 through the seventh capacitor C7, and then rectified into a DC voltage by the eighth diode D3 to continuously supply power to the VCC pin of the second control chip U2; the voltage amplitude of the auxiliary winding is proportional to the voltage at the boost output end. The voltage dividing network attenuates the induced voltage in proportion, and a smooth DC signal is generated after rectification by the eighth diode D3. The second control chip U2 compares with the reference voltage through the internal error amplifier, and adjusts the switching frequency or duty cycle of the second field-effect control switch tube Q3 in real time to compensate for input voltage fluctuations or load changes.

[0058] It can be understood that for the boost circuit in this embodiment, only a very small current is required at the HV pin to start the control chip, which can avoid the static loss of the starting resistor in the traditional solution; during the operation stage, it is completely powered by the voltage doubler rectifier circuit of the auxiliary winding without an external auxiliary power supply, and the conversion efficiency and power supply voltage stability are high; the voltage doubler rectifier network can adapt to different auxiliary winding voltage amplitudes through the parameter matching of the seventh capacitor C7, the seventh resistor R2, and the eighth resistor R11, generating a stable VCC voltage, thereby supporting the design requirements of diverse inductor parameters and improving the design flexibility of the system; the seventh capacitor C7, the seventh resistor R2, and the eighth resistor R11 are replaced with general-purpose surface-mounted components instead of a dedicated power supply module, reducing the cost by more than 70%. At the same time, vulnerable parts such as electrolytic capacitors and transformers are discarded, greatly extending the service life, and the reliability reaches the industrial grade standard. Those skilled in the art can adjust according to actual needs. For example, replace the eighth diode D3 with a Schottky diode to reduce the rectification voltage loss and improve the light load efficiency; or connect a zener diode or a TVS tube in parallel at the output end of the voltage doubler rectifier network to expand the overvoltage protection range; or replace the seventh capacitor C7, the seventh resistor R2, and the eighth resistor R11 with a π-type filter network to enhance the high-frequency noise suppression ability; or use a digital control chip to replace the analog architecture and dynamically calibrate the voltage division ratio through software.

[0059] Further, referring to Figure 1 and Figure 5 In a specific embodiment of the present invention, the boost circuit 5 further includes a voltage sampling circuit and a current sampling circuit; the voltage sampling circuit includes a fourth voltage dividing resistor group and an eighth capacitor C9, and the fourth voltage dividing resistor group includes resistors R34, R35, R36, and R37 connected in series, which are connected across the positive electrode of the sixth capacitor EC1 and the ground; the voltage feedback terminal FB pin of the second control chip U2 is connected to the sampling node between the resistor R36 and the resistor R37, and is grounded through the eighth capacitor C9; the current sampling circuit includes a ninth resistor R33, a tenth resistor RS1, an eleventh resistor RS2, and a ninth capacitor C8; the resistors RS1 and RS2 are connected in parallel between the source electrode of the second field effect control switch tube Q3 and the ground, one end of the ninth resistor R33 is connected to the source electrode of the second field effect control switch tube Q3, and the other end is commonly connected to the current feedback terminal CS pin of the second control chip U2 with one end of the ninth capacitor C8, and the other end of the ninth capacitor C8 is grounded. The working process is as follows: the 400V voltage at the output end of the boost circuit is divided by the fourth voltage dividing resistor group R34 - R37, and a feedback voltage signal is generated at the node between the resistor R36 and the resistor R37. After filtering out high-frequency noise through the eighth capacitor C9, it is input to the FB pin of the second control chip U2. The second control chip U2 dynamically adjusts the PWM duty cycle through an internal error amplifier to stabilize the output voltage at 400V; when the second field effect control switch tube Q3 is turned on, the source current flows through the parallel resistor of RS1 and RS2, generating a voltage signal proportional to the current. After filtering out high-frequency interference through the RC filter network composed of the ninth resistor R33 and the ninth capacitor C8, it is input to the CS pin of the second control chip U2. The second control chip U2 monitors the peak current in real time through an internal comparator, and immediately shuts off the drive signal when the current exceeds the set threshold to achieve overcurrent protection.

[0060] Compared with the prior art, the beneficial effects of the present invention at least include: The present invention provides an anti-backflash LED drive circuit. During the startup phase, by utilizing the inherent conduction characteristics of the negative-voltage turn-off device, the bus voltage can quickly supply power to the control chip without external drive, and a small-value voltage-dividing resistor is used to shorten the startup time, solving the delay problem caused by a large-value resistor in the traditional solution. During the operation phase, the auxiliary winding coupled by the inductor continuously supplies power to the control chip and triggers the negative-voltage turn-off mechanism of the negative-voltage turn-off device, completely cutting off the power supply path of the startup circuit, eliminating the static loss of the voltage-dividing resistor, and improving the overall efficiency. After power-off, the negative-voltage turn-off device maintains the off state under the negative voltage difference between the gate and source, physically blocking the path of the residual bus voltage from flowing back to the control chip. At the same time, the main inductor stops oscillating, causing the auxiliary winding to lose power, and the rectifying and filtering circuit stops outputting. The power supply of the control chip gradually returns to zero with the natural discharge of the energy storage capacitor. The dual mechanisms ensure that the drive circuit is completely turned off, avoiding the intermittent restart of the LED lamp beads caused by the residual energy of the capacitor.

[0061] Furthermore, by setting a zener diode between the gate and source of the negative voltage shutdown device, the trigger threshold of the negative voltage shutdown can be accurately set by clamping the gate voltage fluctuation, avoiding mis-conduction or delayed turn-off problems caused by voltage fluctuations. Especially in the scenarios of input voltage transient or lightning surge, it ensures that the negative voltage shutdown device can still operate reliably under abnormal working conditions, further strengthening the safety isolation ability during the power-off stage and enabling the system to maintain the non-flashback characteristic in a complex electromagnetic environment. The voltage-dividing resistor group adopts a multi-stage series structure. By increasing the number of resistors and optimizing the resistance ratio, the error influence of a single resistor is reduced to less than 1 / 4 of the total error, significantly improving the voltage sampling accuracy. Through the magnetic coupling design of the auxiliary winding and the main winding and the synergistic effect of the rectifier and filter circuit, the energy conversion efficiency and power supply stability are improved. The voltage-doubling rectifier structure and the multi-stage filter capacitor combination in the auxiliary power supply circuit can generate a stable VCC voltage through the synergistic effect of capacitor coupling and resistor voltage division even when the voltage amplitude of the auxiliary winding fluctuates. It can not only improve the voltage stability of the auxiliary power supply, but also expand the input voltage range through the voltage-doubling mechanism, enabling the system to maintain the power supply to the control chip even at low input voltages and avoiding accidental shutdown caused by input voltage drop. The drive circuit suppresses voltage spikes through the freewheeling of the fifth diode. The sixth diode and the resistor network cooperate to accelerate the turn-off of the MOS transistor and suppress oscillations. Combining the rapid release of inductive energy and the negative voltage shutdown to block the reverse injection path, the power-off flashback is eliminated. High-precision constant voltage and constant current control is achieved through the cooperation of the voltage-dividing resistor group and the source resistor. The multi-stage voltage-dividing resistors are connected across the output terminal and combined with the filter capacitor to suppress noise and stabilize the voltage. The current sampled by the source resistor is filtered by the capacitor in real time to limit the current and prevent overload. The boost circuit realizes a stable high-voltage output under wide voltage input through the cooperative design of closed-loop control and the auxiliary winding. The second control chip dynamically adjusts the duty cycle of the MOS transistor to maintain a constant output voltage, adapting to the high-voltage LED drive requirements. The auxiliary winding combines with the voltage-doubling rectifier circuit to continuously supply power to the control chip, replacing the traditional starting resistor structure, eliminating static losses and improving efficiency. The capacitor coupling and resistor voltage division network suppress interference and ensure accuracy.

[0062] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. An anti-backflash LED driving circuit, characterized in that, Comprising: A power supply module (1) for converting an input voltage into a bus voltage; A drive control circuit (2) including a first control chip (21), a first field-effect control switch tube (22), and a first power inductor (23); the input end of the first field-effect control switch tube (22) is connected to the output end of the power supply module (1), the output end is connected to the LED load through the first power inductor (23), and the control end is connected to the drive end of the first control chip (21); A startup circuit (3) including a negative voltage shutdown device (31); the input end of the negative voltage shutdown device (31) is connected to the output end of the power supply module (1), and the output end is connected to the power supply end of the first control chip (21); An auxiliary power supply circuit (4) including an energy conversion module magnetically coupled to the first power inductor (23) for converting the induced AC voltage into a DC voltage and supplying power to the first control chip (21); When the voltage difference between the control end and the output end of the negative voltage shutdown device (31) is lower than the shutdown threshold due to the DC voltage, the negative voltage shutdown device (31) shuts down, and the first control chip (21) is converted to be continuously powered by the auxiliary power supply circuit (4); when the power supply is cut off, the voltage difference between the control end and the output end of the negative voltage shutdown device (31) remains lower than the shutdown threshold to maintain the shutdown, blocking the power supply circuit of the bus residual voltage to the first control chip (21), and at the same time the first power inductor (23) stops oscillating to cause the auxiliary power supply circuit (4) to lose the maintaining voltage, realizing the non-flashing extinguishing of the LED load.

2. The anti-backflash LED driving circuit according to claim 1, characterized in that, The startup circuit (3) further includes a first diode, a first voltage dividing resistor group, and a second voltage dividing resistor group, the negative voltage shutdown device (31) is a depletion-type NMOS tube, and the first diode is a zener diode; the drain of the negative voltage shutdown device (31) is connected to the output end of the power supply module (1) through the first voltage dividing resistor group, the gate is connected to the output end of the power supply module (1) through the second voltage dividing resistor group, and the source is connected to the power supply end of the first control chip (21); the gate of the negative voltage shutdown device (31) is further connected to the cathode of the first diode, and the anode of the first diode is grounded.

3. The anti-backflash LED driving circuit according to claim 2, wherein, The energy conversion module includes an auxiliary winding (41) magnetically coupled to the main winding of the first power inductor (23), and a rectifying and filtering circuit (42) connected to the auxiliary winding (41).

4. The anti-backflash LED driving circuit according to claim 3, characterized in that, The rectifying and filtering circuit (42) includes a second diode, a third diode, and a first resistor; the second diode is a zener diode, and the regulated voltage value of the second diode is greater than the regulated voltage value of the first diode; the first end of the first auxiliary winding (41) is connected to one end of the first resistor, the other end of the first resistor is connected to the anode of the third diode, the cathode of the third diode and the cathode of the second diode are commonly connected to the power supply end of the first control chip (21), and the anode of the second diode is grounded.

5. The anti-flashback LED driving circuit according to claim 4, wherein The rectifying and filtering circuit (42) further includes a fourth diode and a first capacitor; a first end of the first auxiliary winding (41) is connected to one end of the first resistor through the first capacitor, a second end of the first auxiliary winding (41) and an anode of the fourth diode are commonly connected to ground, and a cathode of the fourth diode is connected to the other end of the first resistor.

6. The anti-backflash LED driving circuit according to claim 1, wherein The drive control circuit (2) further includes a fifth diode, and the first field effect control switch tube (22) is an enhancement type NMOS tube; a drain of the first field effect control switch tube (22) is connected to an output end of the power supply module (1), a gate is connected to a drive end of the first control chip (21), and a source is commonly connected to an input end of a main winding of the first power inductor (23) with a cathode of the fifth diode, and an anode of the fifth diode is grounded.

7. The anti-backflash LED driving circuit according to claim 6, characterized in that, The drive control circuit (2) further includes a sixth diode, a second resistor, a third resistor, and a fourth resistor; an anode of the sixth diode, one end of the second resistor, and one end of the third resistor are commonly connected to a gate of the first field effect control switch tube (22), the other end of the second resistor is connected to a source of the first field effect control switch tube (22); a cathode of the sixth diode is connected to one end of the fourth resistor, and the other end of the third resistor and the other end of the fourth resistor are commonly connected to the drive end of the first control chip (21).

8. The anti-backflash LED driving circuit according to claim 7, characterized in that, The drive control circuit (2) further includes a voltage sampling circuit (24) and a current sampling circuit (25); the voltage sampling circuit (24) includes a third voltage dividing resistor group and a fourth capacitor, and the third voltage dividing resistor group is connected across an output end of a main winding of the first power inductor (23) and ground; a voltage feedback end of the first control chip (21) is connected to a sampling node of the third voltage dividing resistor group and grounded through the fourth capacitor; the current sampling circuit (25) includes a fifth capacitor and a sixth resistor; one end of the sixth resistor is connected to a source of the first field effect control switch tube (22), and the other end is commonly connected to a current feedback end of the first control chip (21) with one end of the fifth capacitor, and the other end of the fifth capacitor is grounded.

9. The anti-backflash LED driving circuit according to claim 1, characterized in that, It further includes a boost circuit (5), and the boost circuit (5) includes a second control chip, a second power inductor, a seventh diode, a second field effect control switch tube, and a sixth capacitor; a first input end of the second control chip is connected to an output end of the power supply module (1), a second input end is connected to a first end of an auxiliary winding of the second power inductor, and a drive end is connected to a gate of the second field effect control switch tube; a second end of the auxiliary winding of the second power inductor is grounded; a first end of a main winding of the second power inductor is connected to the output end of the power supply module (1), a second end is connected to a drain of the second field effect control switch tube and an anode of the seventh diode, a cathode of the seventh diode is connected to a positive electrode of the sixth capacitor, a source of the second field effect control switch tube is grounded, and a negative electrode of the sixth capacitor is grounded.

10. The anti-backflash LED driving circuit according to claim 9, wherein The boost circuit (5) further includes a seventh resistor, an eighth resistor, a seventh capacitor, and an eighth diode; one end of the seventh capacitor is connected to the first end of the auxiliary winding of the second power inductor, and the other end is connected to one end of the seventh resistor and one end of the eighth resistor; the other ends of the seventh resistor and the eighth resistor are commonly connected to the anode of the eighth diode, and the cathode of the eighth diode is connected to the second input end of the second control chip.

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